The present invention relates to a Laterally Diffused Metal Oxide Semiconductor (LDMOS) transistor which can be connected to other devices in such a way that the resulting total device has a high bandwidth and high output power with a small surface area.
When connecting LDMOS transistors to other circuits, it is of great importance that the transistor can be matched to the impedance of the circuits to which it is connected, for example in order to achieve high power, high efficiency and high linearity. LDMOS transistors are currently constructed as discrete chips that can be matched to the surrounding circuits by means of, for example, matching networks on circuit boards. The connection of the LDMOS transistor to the surrounding circuits is carried out by the use of so-called bonding wires, which severely restricts the bandwidth in the resulting total circuit, depending upon the length of the bonding wires that is required by known technology.
There is thus a need to be able to match an LDMOS transistor to the impedance of other circuits in a way that does not restrict the bandwidth to the same extent as in previously known solutions.
This need is met by the present invention by providing an LDMOS transistor comprising gate, source and drain, and an earth plane located under these, where the transistor""s earth plane has been given such an extent in the lateral direction of the transistor that an additional component of chip type, for example a matching network or a power amplifier, can be mounted on it, arranged in such a way that the LDMOS transistor and the additional component of chip type have a shared earth plane, while at the same time the LDMOS transistor and the other component(s) are so close to each other that the length of the connections does not restrict the bandwidth in the same way as the connections in previously known solutions.